1. Field of the Invention
The present invention relates to a key assembly, and to a keyboard comprising an array of such key assemblies, in which the keytop elements of the key assemblies are retractable, being translatable between a raised active position and a retracted, "low profile" inactive position.
2. Description of the Related Art
In the field of computer technology, there has been a continuing evolution of efforts to reduce the size and weight of computer equipment, under the impetus of ongoing developments in microcircuitry products resulting in memory and processor chips of exceedingly small size and exceedingly high memory capacity and processing (clock speed) characteristics, respectively.
These efforts to reduce the size and weight of computer equipment, particularly in personal computers such as notebook, palmtop, and personal digital assistants, have also been focused in part on the mechanical user interface, which typically includes a keyboard.
The keyboard may be of various types, including a full-size or extended keyboard, or the keyboard may comprise, particularly in the case of palmtop and sub-notebook computers, a keypad having a relatively smaller number of key elements than full-size or extended keyboards.
In particular, there is a need to provide keyboards having improved "low profile" character, in respect of the height of the keytop elements from the base surface of the keyboard. The keytop elements must of course be of "raised" character during the operation of the keyboard, in order to be depreciable, or actuatable, by the fingers of the keyboard user. The keytop element is depressed by the user's finger, and typically associated with such element is a switch or contact structure which in the depressed position of the keytop functions to produce a signal yielding the desired keying character. There have been various prior art efforts to reduce the thickness or profile height of the key assemblies of the keyboard. While these and other efforts to reduce the size and increase the compactness of computer keyboards have variously produced keyboards of improved character, there is a continuing need in the art to provide further improved keyboards having superior size, weight, and ergonomic characteristics.
U.S. Pat. No. 4,096,364 issued Jun. 20, 1978 to W. J. Lynn, et al describes a keyboard having a plurality of domes which are depressible by buttons having actuator portions. The domes have a snap initiator at the top thereof, so that buttons having a relatively tiny actuator portion, a pair of raised surfaces, serving as actuator portions, or other shaped actuators can be utilized. The dome and keyswitch structure is shown in FIG. 5 of the patent in one embodiment. The patent discloses the use of a hidden pivot element for stabilization of the keyswitch.
U.S. Pat. No. 4,029,916 issued Jun. 14, 1977 to P-J Chu describes snap-action push-bottom switches having a pre-strained dome-shape spring contact plate undergoing snap-action after a predetermined amount of applied for, and snaps back after removal of the force. A living hinge structure is described, involving a combined switch and tactile element.
U.S. Pat. No. 3,982,081 issued Sep. 21, 1986 to H. W. Demler, Jr. discloses a keyboard having integral switch and spring members formed from a single piece of plastic material or sheet metal.
U.S. Pat. No. 4,315,114 issued Feb. 9, 1982 to J. H. Monti, Jr. describes a telephone push button dialer-keyboard, comprising key elements which are adapted to be actuated on depression. The key elements are hinged to a cross brace or transverse support member, which in turn has hinged thereto a plurality of buttons of one alignment. The keyboard utilizes hidden pivot arms and living hinge stabilizers.
U.S. Pat. No. 4,582,967 issued Apr. 15, 1986 to D. D. Burmit, et al discloses a keyswitch formed in a one-piece cantilever assembly with an actuated arm connected by a living hinge to the body member, with the keyswitch being insertable between the top cover plate and the substrate, and the body member serving to maintain the spacing between the substrate and the cover plate. The under side of the keyswitch carries a bell-shaped actuator bar contacting a subjacent contact element or dome. The actuator arm features a projection on its upper surface which extends through an aligned aperture in the top cover plate to receive the T cap.
U.S. Pat. No. 4,827,243 issued May 2, 1989 to S.-C. Cheng discloses a keyboard button structure as shown in the exploded view of FIG. 1 in the patent. Each key button has a U-shaped guide plate on its lateral sides with a hollow guide pan extending downwardly from the button and a pall-like sheet at its bottom end. Holes in the housing panel receive the button, and a rubber dome element 6 is interposed between the button and panel to provide button return.
U.S. Pat. No. 4,764,770 issued Aug. 16, 1988 to R. L. Church describes a stabilized molded rubber keyboard, in which the keyboard comprises a rubber base sheet that directly overlies a PC board and a series or rubber keys or key caps integral with the base sheet. On the upwardly recessed bottom surfaces of each key is provided switch-contact members. A stabilizing membrane snugly engages each key, and is flexible along a Z axis and is sufficiently restrained in x and y directions to limit key movement to a substantially strictly linear movement with reference to the PC board switch contacts. The keys described in this patent are of a non-pivoting type.
U.S. Pat. No. 4,618,744 issued Oct. 21, 1986 to K. M. Pope, et al describes a keyboard including elastomeric dome keypads. Rocker mounted keys as shown in FIG. 2 of the patent are positioned to actuate the domes of the keypad. The patent describes the rotary mounting means for attaching the keys to a bezel position to overly the elastomer dome keypad, such that the travel path of the keys is arcuate. The rotary mounting means may comprise at least one aperture formed in the flange of each of the keys and a corresponding protrusion aligned with the aperture in the flange and extending outwardly from the bezel on the side thereof facing the elastomer dome keypad.
U.S. Pat. No. 4,430,531 issued Feb. 7, 1984 to A. J. Wright describes a keyboard having snap disc switching elements with domed central portions and peripheral foot portions. In this keyboard, each disc is joined by a single strap to a pair of tabs and is positioned on a supporting substrate by means of holes in the strap and mating locator pins. The pins may be employed for fastening the disc to the substrate. A sheet of resilient material is placed over the discs and hingedly mounted keys act on the disc through the resilient sheet.
U.S. Pat. No. 4,359,613 issued Nov. 16, 1982 to C. E. Rooney discloses a keyboard including a plurality of keys which are individually supported for selective depression thereof, wherein the keys are operably coupled to output means by structure including an elongated, resilient element for each key and having a shiftable operating portion. Means operably interconnect keys and associated elements for shifting of the operating portions of the element in response to depression of specific keys. In one embodiment the keyboard includes a plurality of keys with an elongated, generally horizontally extending support arm assembly secured to each key, with certain of the arms extending in a first direction and with others extending in a second direction, and with the respective arms being mounted for pivotal movement about generally horizontal axis spaced from the associated keys.
U.S. Pat. No. 4,359,612 issued Nov. 16, 1982 to C. E. Rooney describes a keyboard and structure thereof operably coupling the keys with output means. The coupling structure includes an elongated, resilient element associated with each key, together with means for shifting the element in response to depression of associated key, and means for disengaging the element in its shifted condition and allowing same to "snap back" to an original rest position. Output means include a microswitch which senses the shifting movement of the resilient element, and develops and electric output signal. U-shaped shifting members are utilized which engage U-shaped resilient elements supporting one or more upstanding encoding posts, to facilitate pocking of the U-shaped element and disengagement from the shifting member, to effectuate the snap-back action.
U.S. Pat. No. 4,351,988 issued Sep. 28, 1982 to F. E. Albright discloses a keyboard assembly in which the switch actuating means for the keys is of arcuate configuration cantileveredly extending beneath the key from one side thereof to an opposite side thereof and positioned to engage the switching means when the key is depressed.
U.S. Pat. No. 4,190,748 issued Feb. 26, 1980 to G. B. Langford describes a keyboard switch assembly utilizing membrane switches and rubber dome tactile members. Keyswitchs are operated by hinged key actuators in the disclosed keyboard switch assembly.
U.S. Pat. No. 4,032,729 issued Jun. 28, 1977 to C. W. Koistinen describes a low profile keyboard switch utilizing hinged actuator and cantilevered beam snap action contacts.
U.S. Pat. No. 3,800,104 issued Mar. 26, 1974 to W. A. Lien, et al describes a low profile keyboard switch assembly including pivoting stabilizer having a pivot point which is part of the previous row of buttons, and in which the pivot arm is hidden. In the disclosed assembly, a single sheet of conductive material is fabricated to include a cantilevered arm having two portions, including a deformed first portion providing a relatively shorter support arm and a remaining, relatively longer tongue member stressed into a convex or concave configuration. At the free end of the cantilever is provided a contact adapted to engage the terminal.
U.S. Pat. No. 3,574,335 issued Apr. 13, 1971 to H. Ricke describes a keyboard having interconnected keys, as shown in FIG. 2 of the patent, in which each key means includes a finger piece, a connecting arm and a support arm, with the support arm of each key means located under the finger piece to the respective adjacent preceding key means of the row, and having a guide means such as rectangular opening for guiding the connecting arm on the preceding key means passing through the opening.
U.S. patent application No. 07/993,192 filed in the name of David A. Bruner, and now allowed, discloses a low profile tactile keyswitch including a horizontally positioned elastic column spring which buckles under an axial load to provide a tactile field for the keyswitch. The ends of the elastic column spring are maintained between two spring holders which are urged together as the key button is pressed, with stabilizing arms pivotally attached to the key button being used to stabilize the key button and also to carry extensions which engage the spring holders to move them together as the key button is depressed. In such keyswitch, lowering of the key button may be effected without placing the elastic column spring under added compression, when the keyswitch is in an inactive configuration.
Accordingly, it is an object of the present invention to provide a key assembly, and a keyboard comprising an array of such key assemblies, which are highly compact in character.
It is another object of the invention to provide a key assembly and keyboard of such type, wherein the keytop elements are retractable from (i) a raised active use position (:in which the keytop elements are selectively manually actuatable to input keying characters or other information into the device with which the keyboard is associated, to (ii) a retracted, "low profile" inactive position.
Other objects and advantages of the invention will be more fully apparent from the ensuing disclosure and appended claims.